摘要:

In device‐manufacturing technology, it is important to understand why dielectric films crack. With this objective in mind, we have constructed an apparatus for measurement of thermal stresses in thin films (25–500 °C), obtained results on various reactively plasma deposited (RPD) Si‐N and CVD SiO2films, and developed a model which quantifies the cracking resistance of different types of RPD Si‐N films. Measurements were made of the coefficient of thermal expansion &agr; (T), which increases on going from SiO2→Si3N4→SiN→Si and the intrinsic stress, which is compressive for RPD Si3N4, nearly zero for thermal SiO2and tensile for RPD SiN and CVD SiO2. The cracking resistance of Si‐N film at a given temperature is functionally related to its density, intrinsic stress, thermal mismatch with Si, and the deposition temperature.

ISSN:0021-8979    

DOI:10.1063/1.325084

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Annealed etched molybdenum and tungsten wires were field evaporated to perfection in a specially designed field‐ion microscope through which a laser beam could be focused onto the perfect metal emission end form or along the wire shank. Irradiation utilizing aQ‐switched laser at fluences between 22 and 35 J/cm2produced residual effects ranging from increasing numbers of lattice vacancies and vacancy clusters to massive deformation, cavitation and spallation, and melting. The results of increasing vacancy concentration with increasing laser fluence for molybdenum and tungsten were compared to similar observations in explosively shock‐loaded molybdenum in concluding that laser shocking can produce residual effects approximately up to several hundred kbar peak pressure. Laser irradiation of electron transparent molybdenum foils also confirmed the attendant features of laser irradiation including vaporization, melting, and shock‐induced spallation by direct observations in the transmission electron microscope. Dislocation substructures identical to those observed following explosive shock loading of molybdenum were also observed in the laser‐irradiated molybdenum foils.

ISSN:0021-8979    

DOI:10.1063/1.325085

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Two techniques of approximating the transient response of a double‐heterojunction light‐emitting diode or diode laser in which there is a nonzero recombination velocity at the heterojunctions are compared to the results of a recently published exact series solution for the transient behavior of such structures. It is shown that both approximations can lead to large quantitative errors—one overestimating and the other underestimating the speed of response—when the active region is wide and the interface recombination is large, but that both approximations are useful and yield similar results when the active region is narrow and interface recombination is small. For devices with narrow active regions and small recombination velocities, it is shown that the transient response can be represented as a single exponential with a characteristic lifetime given by &tgr;[1+(Sv1+Sv2)/D]−1, whereSviandDare the normalized interface recombination velocities and active region width, respectively.

ISSN:0021-8979    

DOI:10.1063/1.325086

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The photocurrent of sintered AgBr microcrystals of high dark conductivity has been measured at room temperature by using a polarization technique of mobile silver ions. Under the condition in which mobile silver ions were polarized, first, a negative photocurrent was observed and, consequently, this negative photocurrent was reversed to a positive one; that is, a ’’photocurrent‐inversion effect’’ has been found. This negative photocurrent and the inversion effect of the current were explained by the theory of photographic sensitivity and the experimental estimation of the range of photoelectrons (?5×10−4cm) in this sintered AgBr. It has been concluded that excess silver ions could be regarded not only as being significant for the electron traps in the surface region, but also as being the electron traps whose distribution could be varied by external voltage.

ISSN:0021-8979    

DOI:10.1063/1.325087

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

We have developed a technique for fabricating polycrystalline thin films of CdS onz‐cut LiNbO3. A single film will show a light‐to‐dark–conductivity ratio of approximately unity with very high sheet resistance after curing. To make a good photoconductor, a second film is then deposited. This film is protected during the subsequent curing from out‐diffusion from the LiNbO3by the first film and develops a light‐to‐dark–conductivity ratio of 10 000 in room light with a sheet conductivity of 10−10s/&laplac; mcd. Films produced by this layered process also possess a remarkably large conductivity‐modulation dependence (20&percent;) on the square of an impressed electric field provided by a traveling surface acoustic wave in the LiNbO3substrate.

ISSN:0021-8979    

DOI:10.1063/1.325088

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

It is proposed and experimentally verified that the anomalously high superconducting critical field normal to the surface of NbN films possessing a column‐void microstructure isHc3, the field appropriate for surface superconductivity. It is also proposed that because the coherence length is much less than the lateral column dimension that the resistivity of the column and not the film enters calculations of the Maki parameter &agr;. A previously noted discrepancy in &agr; is removed by these proposals.

ISSN:0021-8979    

DOI:10.1063/1.325089

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The behavior of a superconducting loop containing two Josephson junctions has been studied by means of computer simulations. It is found that a current‐biased system can exhibit various dynamical modes in which flux quanta alternately enter and leave the loop through the junctions. The nature of these coupled oscillations and their dependence on device parameters are discussed.

ISSN:0021-8979    

DOI:10.1063/1.325090

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Measurements of the magnetic field dependence of Fiske steps and ’’zero‐field’’ steps in Nb–Nb oxide–Pb Josephson junctions are described. By the use of a simple variable dc bias scheme, the measured ac volt‐ampere characteristics are made to clearly exhibit the step structure even in the presence of a large dc Josephson current. A comparison with the theory of Kulik for the magnetic field dependence of Fiske steps is shown and the correlation is very good for smallL/&lgr;jratios. Deviations for larger ratios include the appearance of zero‐field steps.

ISSN:0021-8979    

DOI:10.1063/1.325091

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The in‐plane susceptibility &khgr;pof several amorphous sputtered GdCoMo films shows a minimum of ∼3×10−4emu at the compensation temperature. This value is accounted for theoretically by the classical antiferromagnetic susceptibility relation. The contribution to the in‐plane susceptibility of composition inhomogeneities is also calculated. The fact that such an increase in susceptibility is not observed in experiment indicates the films are quite homogeneous magnetically. Comparison of the anisotropy in films prepared at high and low deposition rates indicates the effect of rate on anisotropy is weak.

ISSN:0021-8979    

DOI:10.1063/1.325092

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The anisotropy field as measured by resonance is calculated for a coherent assembly of small magnetic particles possessing both crystal and shape anisotropy. The theoretical results are compared with experimental data on precipitated cobalt and magnesioferrite particles.

ISSN:0021-8979    

DOI:10.1063/1.325093

出版商:AIP    

年代:1978

数据来源: AIP